Electrical heating elements for use under floor are widely used. In one arrangement the heating element comprises a flexible, electrically insulated polyester coated element in the form of an elongate sheet formed of top and bottom overlying layers of a polyester material where the element consists of two electrodes or bus bars running parallel the length of the element between the layers along the side edges. A row of conductive ink strips are printed onto the top surface of the bottom one of one layer of the polyester at right angles to the electrodes, contacting the electrodes thereby setting up parallel electrical heating circuits across the elongate sheet. The electrodes applied on top of the printed conductive heating strips can be formed of tinned copper and may cover a printed layer of a silver ink applied onto the edges of the bottom layer. The printed heating conductors and the bus bars are covered by the top layer.
Examples are shown in WO 2008/063173 (Seo) assigned to Carbonic Heat Corp and published 29 May 2008, WO 2007/008734 (Seo) assigned to Carbonic Heat Corp and published 18 Jan. 2007 and in WO 01/65891 (Marstiller) assigned to Calorique Ltd and published 7 Sep. 2001.
In another arrangement the heating element comprises a continuous serpentine heating wire embedded in or carried by a scrim to form a layer which can be laid over a sub-floor with the wire as part of the layer.
Such heating elements are well known and widely used for many different end uses. One end use which is preferred but not the only end use with which the present application is concerned is that of heating tile or other floors where the heating element is located between the sub-floor and the covering material with the floor adhesive applied over the heating element. The element can also be used with other types of covering layer such as concrete.